Origin & Evolution of Life: September 2008

The NASA Exoplanet Science Institute announces the introduction of the Sagan Postdoctoral Fellowship Program and solicits applications for fellowships to begin in the fall of 2009.

The Sagan Fellowships support outstanding recent postdoctoral scientists to conduct independent research that is broadly related to the science goals of the NASA Exoplanet Exploration area. The primary goal of missions within this program is to discover and characterize planetary systems and Earth-like planets around nearby stars.

NAI's University of Wisconsin team presents a review of iron isotope fingerprints created through biogeochemical cycling in the May, 2008 issue of The Annual Review of Earth and Planetary Sciences. This landmark paper brings together for the first time the co-evolution records of photosynthesis, bacterial sulfate reduction, and bacterial iron reduction in the early Earth. They review data on natural systems and experiments, looking at both abiological and biological processes, and conclude that the temporal carbon, sulfur, and iron isotope record reflects the interplay of changing microbial metabolisms over Earth's history. [Source: NAI Newsletter]

Abstract: Silicate super-earths are rocky planets with masses up to ~10 that of the Earth. They are of astrobiological interest because they are relatively easy to detect around other stars. Tectonics enhances habitability on the Earth by exhuming biologically important elements. Plate tectonics are too poorly understood on the Earth to tell whether this process should occur on larger planets. Still the Gauss' law relationship that surface heat flow scales with surface gravity provides some insight and yields that the geotherm expressed in terms of pressure is to the first order invariant to planetary size.